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Rostra Electric Cruise Control Installation

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Joined: 19 Oct 2012
Posts: 16
Location: Sierra Nevada Mountains, California

PostPosted: Tue Nov 13, 2012 2:05 am    Post subject: Rostra Electric Cruise Control Installation Reply with quote

Disclaimer of Liability

If you are using this information to help you install a cruise control in your motorcycle, you are an adult and are taking complete responsibility for your own actions and choices. If you are not an adult and/or are not taking responsibility for your own actions and choices, read no further. The author will not accept any responsibility or liability for your use of this information.


This is a description of installing a Rostra Cruise Control (model# 250-1223) in a 1993 K1100LT. Many of the wiring and physical details described herein will apply directly to all other K1100s. Installations in other brands and models of motorcycles may benefit somewhat less but there should still be useful information for all who intend to install this cruise control.

I installed the Rostra Cruise Control model 250-1223 (hereafter “CC”) in my ’93 LT as the previously-installed cruise control (Audiovox CCS-100) had failed -> twice <- in a year. The price was right on the Audiovox, but the day-to-day of it was a bit weak and two failures in one year were enough for me. I thought, let’s just spend the money and get the electric-powered CC. No vacuum issues (think high load, high speed at higher elevation which means lower vacuum), and also a three year warranty on the 250-1223. And understand, I had all four cylinders pulling vacuum (each through a check valve), two large vacuum storage tanks and 15+ InHg vacuum from the engine. It really doesn’t get a lot better than that so far as I’ve seen in my searches online. Still, I found that high speed travel was sometimes an issue for my sidecar rig. I recognize that my K11 sidecar works *much* harder than a single-track bike, but you should know that the edge is out there, awaiting the vacuum-powered cruise control.

Some background about the context of this installation:
My bike is a 1993 K11LT (ABS I) in combination with an EML GT2000 Sidecar. The sidecar conversion is permanent and includes a change to 14” automobile tires at all three places. The outfit weighs about 150 pounds or so more than the stock K11LT, which of course changes the behavior based on power-to-weight ratio. On the other hand, the 14” tires mean that the overall drive ratio is about 87% of the stock configuration. That is, the LT’s engine is turning RPM / 87% or about 15% faster at a given road speed, giving it more mechanical advantage in a given situation.

This bike/sidecar combination has a number of other things installed in it including: a fuel cell in the sidecar trunk with computer-controlled fuel pump and rider display of gallons/miles remaining, driving lights, intercom wiring and of course the hardware and wiring needed for the sidecar conversion. As a result, many wires, cables and fuel lines not present in other K11's are seen in the photos below.


With the stage set, let’s start with the mechanical elements of the installation. After surveying the possibilities, I decided to place the CC unit in the tailpiece of the bike in order to keep it out of the weather and out of sight. (as I have a large sidecar sitting just over there, the storage loss in the tailpiece was not an issue for me)

Note: The rat's nest of wiring in the tailpiece will be shortened, the Posi-Tap connectors replaced with solder/shrink tubing and generally prettified after I'm confident that everything is as it should be with the installation. That said, the tailpiece will, for me, will be dedicated to the CC, and all the other things that might go in there carried in the sidecar trunk.

Wiring from the front of the bike runs along the inner (center) side of the upper right frame rail and reaches the CC through a hole in the extreme lower / right corner of the front of the tailpiece, just aft of / below the seat hinge. The violet wire from the CC reaches behind the taillight through an existing hole between those two areas.

The CC wiring enters the tailpiece near the rear seat hinge

The CC wiring travels forward along the upper right-side frame tube

Note: Some of the additional hardware/wiring/cabling/fuel lines in this bike are visible here. For example, the AN fuel line and large rubber-wrapped item - a check valve - deliver fuel from the fuel cell in the sidecar trunk to the fuel injection loop of the bike (the same fuel line is seen in the "Cable Bracket" photo). The CC wiring is all in one split-tube, sometimes itself wrapped in shrink tubing.

I ran the CC drive cable forward along the upper left frame rail to above the #1 throttle body. The cable is attached to a bracket that came from the CCS-100. As most folks will not be replacing a CCs-100 installation, I’ll describe the bracket used to secure the cable above the throttle body linkage.

The CC cable passes aft from underneath the fuel tank, just above the fuse block.

The CC cable passes aft along the upper left-side frame tube.

The CC cable passes aft into the tail piece.

Cable Bracket
The bracket (the gold in color part seen in the photo) is basically ‘L’ shaped flat stock with it’s flat side facing to the side, allowing for two attachments to the frame and for a leg directed straight down toward the linkage connection point. The two attachments at the frame are through the gusset that strengthens the frame just above throttle bodies #1 and #2. I drilled two holes through the gusset to attach the bracket. The bracket positions the cable end directly above cylinder #1's throttle body. At the bottom of the vertical leg of the ‘L’ is a 90-degree bend (outboard - to the left from the rider’s position). In the resulting horizontal portion of the bracket is a slot, allowing the cable to be attached by pinching the bracket between the two nuts threaded onto the end of the cable. The end of the cable points straight down at the throttle body linkage. Note that, per the Rostra install guide, the “threads” in the end of the cable are put there by threading a nut onto it, leaving “threads” in the cable outer housing. It’s weird, but it seems to work - just don’t ask those “threads” to pull hard when you attach the cable to the bracket. It works out as this is a friction fit that’s not being pulled outboard, but go lightly on tightening the lock nuts, only far enough to keep them parked despite engine vibration and road shocks. The relative position of the lock nuts on the cable allows the amount of free play in the cable to be finely adjusted. The Rostra install guide “assumes 1/8”. I decided to thread the nuts a bit more onto the cable than was actually needed, leaving some ability to reduce the amount of cable slack later - as the CC seems sensitive to how much slack it has to pull in before moving the throttles.

The bracket securing the end of the CC cable directly above the #1 throttle body linkage. Note the extra cable housing projecting below the lock nuts. It allows for fine adjustments to the amount of cable slack later, should that be needed. The fuel line being held aside is the fuel return line to the tank and includes a non-standard AN "T" fitting (blue and red aluminum) that delivers fuel from a fuel cell in the sidecar trunk as described above.

Throttle Body Connection
The cable attaches to the throttle body by means of a hole drilled through the vertical surface of the throttle body linkage. A short bolt through the hole is secured by a “Nyloc” nut and has washers on both sides of the "Eyelet Connector" (included with the CC) and beads. Extra washer(s) are used on the linkage side of the eyelet connector to keep it from rubbing on the linkage as it rotates. The nut is tightened enough to be secure but also to allow it to rotate freely. In order to keep the beads from becoming mixed up in the nearby hardware and still allow them to provide a bit of slack, I put a bit of plastic tubing around most of the beads to force them to be more-or-less straight up toward the cable bracket attachment.

Attachment of the bead chain to the #1 throttle body linkage.

The relationship of the cable bracket and the #1 throttle body. The black tubing keeps the chain pointed at the bracket above at all times, avoiding the chance of the beads becoming tangled in anything nearby. (the dual “Bead Chain Connectors” are present because I was too durn lazy to replace the CCS-100 beads from the throttle body and they were not quite long enough. Wink )

Control Switch
Rather than the standard Rostra control switch, which is small and not weatherproof, I used two K11 switches, one for power on/off and the other for set/resume. They are easy to use with gloves on, they look like the other switches on the bike and they are designed to live out in the weather. The switches are installed in a small plastic project box. The project box is mounted to a threaded shaft (these can be purchased as a threaded stud or similar) that is secured in the mirror mounting hole on the left side switch cluster by means of Nyloc nuts, allowing its vertical location and resistance to rotation (when the switches are pressed) to be easily set. The project box is located over the fast idle lever and is spaced (by adjusting the location of Nyloc nuts on the shaft) just out of contact with the idle lever. This puts it as close to the rider’s left hand as can be without it interfering with the fast idle lever or anything else. Both the set/resume and on/off switches can be comfortably pressed without the rider taking her hand off the left grip.

The control switch mount. A threaded shaft secured by Nyloc nuts and sheathed in a short length of fuel line (for a clean appearance). Note the wiring leaving the project box on the other side and running down along the handlebar with the stock wiring harness.

The power switch is simple two position on-off (4-way flasher or similar). The set/resume switch needs to be momentary (i.e. works as long as you hold it down) so an LT windscreen up/down switch works for that. The power switch just puts 12v to switch the power relay (see below). The set/resume switch puts 12v onto either the ‘set’ or ‘resume’ wire. So, it can be fed from any ignition-switched 12v and have the yellow and dark green from the CC connected to it. As the power switch needs a 12v source, that same source can be used to feed the ‘set’ and ‘resume’ wires to the CC.


First, a couple of notes about electrical supplies. In general, all connections are soldered and shrink-tube covered. Connections that may need to change are done with “Posi-Tap” brand connectors. I think these are worth the extra cost over the crimp connectors supplied with the CC.

I used relays to supply the main power, brake signal and clutch lever signals to the CC. The relays I chose are “HELLA 007794301 Weatherproof 20/40 Amp SPDT Mini Relay with Bracket” that I bought from Amazon ( http://www.amazon.com/gp/product/B003TEO9GU/ref=oh_details_o00_s00_i00 ) for about $5.27 each. These are SPDT (Single Pole Dual Throw) relays which means that they can either connect or disconnect a circuit when energized.

The electrical pin-out of the relays used in the installation. The relays are marked with both the standard numbers( 30, 85, etc..) and with Hella’s convention of 1 - 5.

Main Power Relay
The main power source for the CC comes directly from the battery. I took this approach so that the (up to) 10amp draw of the CC is not combined with any other load. Yeah, it may just work out, but for an investment of about 5 bucks and 15 minutes of time to wire it up, the CC is separate from all that. I fused the (+) side of the battery lead near the battery to keep the wiring from going up in smoke should the wire be worn through between there and the CC wiring.

The main power relay is switched by the on/off switch in the “Control Switch” and feeds the brown power wire to the CC.

Note: the safety wire visible behind the relays is left over from securing the two vacuum tanks in the previous CCS-100 installation and will be removed.

Clutch Lever Switch Relay
The K11’s clutch lever switch operates by connecting ignition-switched 12v to the engine starter pushbutton so that the engine cannot be started unless the clutch is pulled in (in the case of the bike being in gear). So, using the “downstream” side of the clutch lever switch to energize the relay means that pulling the clutch in triggers the “NSS” safety behavior of the CC. The relay in this case connects the light green wire from the CC to ground, disengaging the CC.

Brake Light Relay
There are so many reports of weird behavior related to the brake light that I decided to separate the CC from all that with a relay. In this case, the grey/yellow wire in the tail light switches the relay to “open” (or float, i.e. disconnected from everything) the violet wire to the CC. According to the Rostra install instructions, the violet wire can either be set to 12v or to “open” (i.e. disconnected) in order to disengage the CC. I chose the “open” approach rather than 12v as it allowed simpler wiring. The CC senses the difference between its red and violet wires. If there isn’t 12v difference, the CC disengages. That’s why either 12v or “open” on the violet wire do the job.

The brake light relay in place behind the taillight. The extra connections on the tail and brake lights are an installation of “Run-n-Lights” and do not affect the CC installation.

Speedometer / VSS
The CC reads the bike’s speed from the speedometer sensor. The sensor has two wires, yellow and brown, and has a connector under the right side cover. According to reports online, either wire can be used to provide VSS to the CC. I used the yellow as normally brown is “ground” in BMW schematics. I know, it doesn’t matter, but there you are.

The (temporary connection to the) VSS signal from the speedometer sensor connector located under the right-side sidecover.

Switch Settings

The choices of switch settings are:
Gain, Pulses / Mile, Engine & Setup Timer / VSS Source / Transmission / Control Switch.

Gain (switch 1 = 1, switch 2 = 0)
I set the gain to “Low” after test rides. It provides a strong-but-not-too-strong pull and can hold/attain high speed while traveling uphill.

Pulses / Mile (switch 3 = 1, switch 4 = 1, switch 5 = 0, switch 6 = 0)
Reports online have the K1100 speedometer sensor generating about 4900 pulses per mile (PPM). As my bike has 14” tires, more pulses happen per mile, about 15% more, I intended to set the PPM to 6000. As it turned out, I mistakenly set PPM to 8000. The 8000 setting is working well but I’ll soon be testing the 6000 setting to see if it offers any improvement.

Engine and Setup Timer (switch 7 = 0, switch 8 = 1, switch 9 = 0)
I set this to “6 cyl / low” after experimentation. The lowest setting (“8 cylinder / low”) had the bike taking too long to reach the set speed from a slower speed) Note that a mistaken setting of the dip switches had me trying out “6 cyl / extra high” very briefly. It was very exciting - avoid making this mistake yourself. This setting and the “Gain” setting are the two that will likely differ most between my installation on a sidecar outfit and yours on a “normal” ( Smile ) bike.

VSS Source (switch 10 = 0)
The K11 speedometer sensor on the K11 generates a sine wave signal.

Transmission (switch 11 = 0)
I chose the manual transmission setting as I am using the clutch lever switch.

Control Switch (switch 12 = 0)
The “momentary on” nature of the set/restore switch I used dictated the “open” switch setting.

Well, there you have it. The CC engages from about 35mph indicated and above. It accepts a set speed quickly and without jerking. It resumes smoothly and quickly. The bike will pull high speeds uphill and will accelerate (by holding the "Resume" switch down) while at high speed going uphill (this is what the vacuum CCS-100 would never reliably do).

I hope this is helpful to someone. I'm happy to answer questions about details not included in this write-up.



UPDATE 11/13/12:
Various minor edits, spelling corrections, etc..
The CC has a "Diagnostic Mode" which allows the installer to see if the various inputs to the device are being received (instructions for using it are in the install guide).
The CC will not enter diagnostic mode if the NSS (i.e. clutch lever switch) is connected, so maybe leave a way to easily disconnect this lead for future diagnostic needs.
Also, during the diagnostic process, the VSS signal from the speedometer sensor will not cause the CC indicator LED to flash as described, but it works nonetheless.
1993 K1100LT / 1996 EML GT2000 Sidecar
2001 R1150GS

Riddle me this:
Two motorcycles are being ridden down a two-lane road. They are followed by a long line of cars.

What brand are the motorcycles?

Last edited by HenryJonesJr on Wed Nov 14, 2012 2:55 pm; edited 9 times in total
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Joined: 10 Oct 2007
Posts: 4183
Location: Sugar Hill, NH, USA

PostPosted: Tue Nov 13, 2012 6:22 am    Post subject: Reply with quote


That is a great write up. THANKS.

If it is OK with you I would like to move it to the Tech Resources and Stickies section.

John & Cathy

'92 K100RS4V Pearl White
'03 R1100S Boxer Cup
IBA Several-SS1k, BBG, 50CC NYC to S.F.
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Joined: 19 Oct 2012
Posts: 16
Location: Sierra Nevada Mountains, California

PostPosted: Tue Nov 13, 2012 12:50 pm    Post subject: Reply with quote

SugarHillCTD wrote:

That is a great write up. THANKS.

If it is OK with you I would like to move it to the Tech Resources and Stickies section.


Move away, I'm just going to be making a few updates as I remember things I forgot to include...

1993 K1100LT / 1996 EML GT2000 Sidecar
2001 R1150GS

Riddle me this:
Two motorcycles are being ridden down a two-lane road. They are followed by a long line of cars.

What brand are the motorcycles?
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